If you feel like taking up the challenge ...
Is there a way to activate Specular based calculations rather than Metallic, in the Spine URP shaders?
I was reading this.
But even after making the GBA channels pure black.. I still can't successfully mask out specific sections.Instead, the Metallic levels for the material are controlled by the values in the Red channel of the texture, and the Smoothness levels for the material are controlled by the Alpha channel of the texture.
Thanks for your help